class A:
  class Person:
      def __init__(self):
          self.__age = 10

      @property
      def age(self):
          return self.__age

      @age.setter
      def age(self, value):
          if value < 0:
              value = 0
          self.__age = value

      @age.deleter
      def age(self):
          print("del age")
          del self.__age
    
      def __getattr__(self, name):
        return None


  p = Person()
  print(p.age)

  p.age = 19
  print(p.age)

  p.age = -19
  print(p.age)

  del p.age
  print(p.age)
